In recent years, with computers and information communication equipments developing toward high performance, high function and networking, to transmit and process large-capacity information at high speed, operation signals tend to be high-frequency. Therefore, the material for circuit substrates is required to be improved, and it has developed rapidly particularly in those electronic devices using broadband network, such as mobile communication devices.
Among the conventional materials used for a printed circuit substrate, epoxy resins with excellent adhesion characteristics are widely used. However, an epoxy resin circuit substrate generally has relatively high dielectric constant and dielectric loss tangent (the dielectric constant is more than 4, and the dielectric loss tangent is around 0.02), and inadequate high-frequency characteristics, which result in failure in meeting the requirement of high-frequency signals. Therefore, it is required to develop resins with excellent dielectric properties, that is, resins having low dielectric constant and dielectric loss tangent. For a long time, technicians in the field have studied thermosetting cyanate esters, bismaleimide resins, hydrocarbon resins, etc., which have excellent dielectric properties. In addition, polyphenylene ether resins, due to having good dielectric properties and heat resistance, are also studied as high frequency, high speed materials by many technicists, but their applications are much limited because of their high melting point and poor flowability, and prepregs made therefrom have high melting viscosity, which can not meet the requirements of the production process of multi-layer printed circuit boards. By reducing the molecular weight of polyphenylene ether resins, the melting temperature can be effectively decreased and the flowability can be effectively improved, but the heat resistance is also impaired.
The Chinese patent application No. CN1745142A discloses a polyphenylene ether resin composition comprising a polyphenylene ether resin containing vinylphenyl and metavinylphenyl at end groups thereof as the matrix resin, isocyanuric acid triallyl ester as the crosslinking agent, and if necessarily also comprising an inorganic filler and a flame retardant. And, a prepreg and a laminate having excellent dielectric properties and comparatively high glass transition temperature are prepared by impregnation of NE type fiberglass cloth in the polyphenylene ether resin composition. However, because the polyphenylene ether composition uses isocyanuric acid triallyl ester as the crosslinking agent which has a comparatively low molecular weight and is easily volatilized in the process of manufacturing prepregs, it is not good for stably manufacturing prepregs and laminates. In the patent application, it is mentioned that besides PPE, if necessarily olefin resins can also be used as compatilizer to improve the heat resistance, adhesiveness and dimensional stability, but studies on various properties of the cured resin are not mentioned.
The US patent application No. US2009/0247032 discloses a resin composition comprising a polyphenylene ether resin having vinyl bifunctionality as the matrix resin, cyanate ether with naphthalene ring structure, bisphenol A type cyanate resin, brominated flame retardant, and an inorganic filler. The resin composition has exceedingly good flowability and good dielectric properties together with extremely good peel strength, humidity resistance and flame retardance.
The PCT patent application No. WO2006/023371A1 discloses a composition comprising a bifunctionalized polyphenylene ether resin and a unsaturated olefin monomer, which can improve the flowability and the performance after curing of polyphenylene ether resin, but in the patent, performance advantages are not be pointed out for using bifunctionalized polyphenylene ether resin in the field of laminates, and the unsatured olefin monomer used is a compound with a low molecular weight that is also easily volatilizated under high temperature to cause poor processability.
In summary, functionalizing the polyphenylene ether with a low molecular weight is a solution to the problem of heat resistance reduction caused by reduction of molecular weight of the polyphenylene ether. However, while being specifically applied to the field of laminates, how to select proper cross-linking is agent and show the performance advantages of the functionalized polyphenylene ether resin still need to be further studied.